Transfusion-associated graft-versus-host disease (TA-GVHD) can be prevented by irradiating red cell units to inactivate donor lymphocytes. In a prior study, we demonstrated that irradiation damages red cells and that this damage is most readily apparent after maximum permissible liquid storage. On occasion, irradiated red cell storage in this manner is not known. We studied ten subjects in a controlled study comparing irradiated and non-irradiated units after frozen storage. There were no significant differences in vitro or in vivo parameters between the irradiated and non- irradiated units after eight weeks of frozen storage. We have shown, therefore, that red cells can be irradiated and subsequently frozen with no detectable damage to the cells.